/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.alipay.sofa.ark.loader.jar;

import com.alipay.sofa.ark.loader.data.RandomAccessData;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

/**
 * Parses the central directory from a JAR file.
 *
 * @author Phillip Webb
 * @see CentralDirectoryVisitor
 */
final public class CentralDirectoryParser {

    private final static int                    CENTRAL_DIRECTORY_HEADER_BASE_SIZE = 46;

    private final List<CentralDirectoryVisitor> visitors                           = new ArrayList<>();

    public <T extends CentralDirectoryVisitor> T addVisitor(T visitor) {
        this.visitors.add(visitor);
        return visitor;
    }

    /**
     * Parse the source data, triggering {@link CentralDirectoryVisitor visitors}.
     * @param data the source data
     * @param skipPrefixBytes if prefix bytes should be skipped
     * @return The actual archive data without any prefix bytes
     * @throws IOException on error
     */
    public RandomAccessData parse(RandomAccessData data, boolean skipPrefixBytes)
                                                                                 throws IOException {
        CentralDirectoryEndRecord endRecord = new CentralDirectoryEndRecord(data);
        if (skipPrefixBytes) {
            data = getArchiveData(endRecord, data);
        }
        RandomAccessData centralDirectoryData = endRecord.getCentralDirectory(data);
        visitStart(endRecord, centralDirectoryData);
        parseEntries(endRecord, centralDirectoryData);
        visitEnd();
        return data;
    }

    private void parseEntries(CentralDirectoryEndRecord endRecord,
                              RandomAccessData centralDirectoryData) throws IOException {
        byte[] bytes = Bytes.get(centralDirectoryData);
        CentralDirectoryFileHeader fileHeader = new CentralDirectoryFileHeader();
        int dataOffset = 0;
        for (int i = 0; i < endRecord.getNumberOfRecords(); i++) {
            fileHeader.load(bytes, dataOffset, null, 0, null);
            visitFileHeader(dataOffset, fileHeader);
            dataOffset += CENTRAL_DIRECTORY_HEADER_BASE_SIZE + fileHeader.getName().length()
                          + fileHeader.getComment().length() + fileHeader.getExtra().length;
        }
    }

    private RandomAccessData getArchiveData(CentralDirectoryEndRecord endRecord,
                                            RandomAccessData data) {
        long offset = endRecord.getStartOfArchive(data);
        if (offset == 0) {
            return data;
        }
        return data.getSubsection(offset, data.getSize() - offset);
    }

    private void visitStart(CentralDirectoryEndRecord endRecord,
                            RandomAccessData centralDirectoryData) {
        for (CentralDirectoryVisitor visitor : this.visitors) {
            visitor.visitStart(endRecord, centralDirectoryData);
        }
    }

    private void visitFileHeader(int dataOffset, CentralDirectoryFileHeader fileHeader) {
        for (CentralDirectoryVisitor visitor : this.visitors) {
            visitor.visitFileHeader(fileHeader, dataOffset);
        }
    }

    private void visitEnd() {
        for (CentralDirectoryVisitor visitor : this.visitors) {
            visitor.visitEnd();
        }
    }

}
